Preheat the oven to 300ºF. Remove the brisket from the refrigerator and allow it to sit at room temperature for 30 to 60 minutes. Pat it dry thoroughly. Trim off any large chunks of fat on the outside. Cut parallel lines partially through the fat cap about ¼ inch apart, taking care not to slice all the way through to the meat. Repeat in the opposite direction, creating a crosshatch pattern.
Warm the oil in a large Dutch oven over medium-high heat. While the oil is heating, season the brisket generously all over with salt and pepper. Add the brisket to the pot fat side down. Sear until browned on both sides, 3 to 4 minutes per side. Transfer the brisket to a large plate. Reduce the heat to medium.
Add the onions to the pot, season with salt and cook, stirring occasionally, until very tender and turning golden, 11 to 14 minutes. Add the garlic; cook, stirring, until fragrant, 1 minute. Add the sugar, ras el hanout and paprika; cook, stirring, until lightly toasted and fragrant, about 1 minute. Pour in the broth and stir to pull up any browned bits from the bottom of the pot. Remove from the heat.
Place the brisket back in the pot; spread the tomato paste on top. Cover and transfer to the oven. Braise the brisket until the meat is cooked through, about 1 hour 30 minutes. Carefully transfer the brisket to a cutting board and let it rest for 5 minutes. (It may seem tough at this point; don’t worry.) Add the carrots, apricots and capers to the pot, tucking them into the liquid. Thinly slice the meat against the grain. Return the meat to the pot, tucking the slices into the braising liquid. Cover and continue to braise until the brisket is very tender, 1 hour 15 minutes to 1 ½ hours longer.
Taste and season with more salt and pepper, if needed. Just before serving, sprinkle the parsley on top. Serve the brisket with the onions, carrots and apricots.